Microbiology is one of the sciences that has jumped to the fore as a vital source of information in the fight against COVID-19. Studying the microorganisms with which we live (bacteria, viruses, fungi, archaea, and parasites) and that even inhabit our bodies is one of the fields of science that most promises to deliver on the future development of personalized or precision medicine.
Humankind is aware that many of its greatest enemies are, paradoxically, microscopic. In 2015, the World Health Organization (WHO) published a list of the emerging pathogens — all viruses — most likely to cause severe outbreaks. The WHO’s objective was to raise awareness about the need prioritize research in this field. Two years later, the same organization released a list of superbugs, bacteria for which new antibiotics urgently need to be developed. The number of deaths from antibiotic-resistant infections could rise to 10 million by mid-century, according to an expert report commissioned by the British government.
Even so, microorganisms also protect our health and medicine is now looking at how they respond to infections in the hope that our little guests can provide some insight into developing personalized treatments. The collection of microorganisms that live in another living organism is known as microbiota. These microorganisms also contain genetic information, for which the term microbiome has been coined, to ensure our terminology also encompasses the resident genetic material.
According to the Spanish Society for Biochemistry and Molecular Biology, our bodies contain virtually equal parts of bacteria and human cells: we are half human, half bacteria. The microorganisms that constitute the microbiota live on the skin, in the mouth, in the gastrointestinal tract, and in the genitourinary and respiratory systems. In the words of an outreach group at the University of Seville, if we were to line up the bacteria in a human body it could loop the Earth two and a half times.
This micro-universe within us, the microbiota, is a dynamic community that interacts with our cells. Much of our health in general and specifically our immune system’s response to infectious diseases depends on this communication. The Spanish Society for Biochemistry and Molecular Biology estimates that more than 10,000 species of bacteria, of which more than 99 percent are non-pathogenic, inhabit a healthy human body.
A microscopic battle: microbes defending us from disease
Understanding that microorganisms are not always our enemies is important to understanding how our body — including the non-pathogenic microorganisms that inhabit it — fights harmful microorganisms like SARS-CoV-2. As explained in a report prepared by the Roche Institute Foundation, microbiota is fundamental in “the processes of synthesizing essential vitamins, removing toxic compounds, strengthening the intestinal barrier, and regulating the immune system.”
Our immune system has two types of responses: innate immunity, which is the first line of defense against infectious agents; and the response produced by the adaptive immune system, which is specific for each infectious agent and is stored in the memory to prevent reinfection in the future. In other words, it differentiates between “resident” and “transient” microorganisms.
Microbiota and immunity from COVID-19
In the case of viruses, for example, the host (i.e., our body) responds to viral infections by initially activating the innate immune system, as well as the adaptive. As researchers Lisbeth Berrueta, Siham Salmen, and Henry Forestry at Venezuela’s University of the Andes explain in this article, these two mechanisms aim to limit the reproduction of the virus and eliminate the infectious agent. However, viruses have evolved and are able to develop strategies to evade the immune response, as occurs with the SARS-CoV-2 virus, which is responsible for COVID-19.
A recent study conducted by the University of Dundee has identified 28 immune response producing proteins created by SARS-CoV-2. These proteins are fundamental tools in the research to develop diagnoses and help understand how the virus infects us and what material in our cells it attacks.
According to the same study, intestinal microorganisms, in addition to helping regulate different aspects of our health, in cases of SARS-CoV -2 infection would also allow us to prevent potentially dangerous immune system responses that damage our lungs and other vital organs.
It is possible to strengthen the immune system by interacting with those microorganisms that comprise our microbiota. Food is the most direct path to activating these mechanisms. Numerous studies have shown that following a Mediterranean diet improves microbiota diversity and helps reduce the potential inflammatory response.
A path towards precision medicine
Understanding how this immune response works against the virus is fundamental to finding the exact antiviral composition necessary for the vaccines to treat it. This is how microbiology and the study of the human microbiome will allow us to push the limits of personalized medicine in addition to studying opportunistic, potentially pathogenic microorganisms, or those that may interfere with potential treatments. According to Lindsay Kalan, the researcher and biochemist at the University of Wisconsin-Madison, it is “important to understand how the microbiome interacts with its human host before beginning to manipulate it to treat ailments and diseases.”